ABSTRACT: In this paper we analyze the optimal management of a mixed fishery where the harvest is composed of a target and a bycatch species. In contrast to other studies, we have included the selectivity of the fishing gear as a control variable. The fishery is regulated by means of total allowable effort and with 2 different systems of total allowable catch (TAC): an aggregated and a disaggregated TAC. The main result obtained is that in an aggregated TAC program, the selectivity level and the decision to discard depend only upon the marginal profits of both species, but that in the case of a disaggregated program, other factors such as gear selectivity have to be taken into account.